I think there are two things to keep in mind. If the price drop were the direct result of not selling well, how come they are still selling the 2-3 year old WP7.5 HTC Trophy for $180? Why was Verizon's HTC 8X selling for $99 when the Nokia 822 was only $49 and then free? Nokia is most likely subsidizing the cost to try and buy market share. There's a risk, of course, that the low price point could cheapen the brand.
BlackBerry is taking the opposite tack and trying to maintain premium pricing in hopes of keeping an upscale, business oriented brand image. The risk for BlackBerry is that people will see the new BlackBerrys as overpriced and choose a cheaper phone. It's just dueling marketing strategies.